With reference to FIGS. 1, 2 and 3, portions of a conventional positive clutch are shown and generally indicated by reference 10. The positive clutch 10 includes a first clutch ring 12 and a second clutch ring 14. A first plurality of teeth 16 is located on the first clutch ring 12 and a second plurality of teeth 18 is located on the second clutch ring 14. When the positive clutch 10 is engaged, the first plurality of teeth 16 and the second plurality of teeth 18 mesh together such that the first clutch ring 12 and the second clutch ring 14 are connected and can no longer rotate relative to one another. Unlike an exemplary friction clutch (not shown), the positive clutch 10 does not slip when engaged.
In most instances, the first clutch ring 12 is out of rotational alignment with the second clutch ring 14, so the first clutch ring 12 or the second clutch ring 14 must rotate relative to one another to align the first plurality of teeth 16 with the second plurality of teeth 18. More specifically, the first clutch ring 12 includes spaces 20 between the first plurality of teeth 16. Like the first clutch ring 12, the second clutch ring 14 also includes spaces 22 between the second plurality of teeth 18. As shown in FIG. 3, alignment and engagement of the positive clutch 10 requires that the first plurality of teeth 16 moves into the spaces 22 of the second clutch ring 14. Similarly, the second plurality of teeth 18 needs to move into the spaces 20 of the first clutch ring 12. To facilitate alignment and engagement of the positive clutch 10, the spaces 20, 22 are larger than the plurality of teeth 16, 18. The larger the spaces 20, 22, (relative to the teeth 16, 18 respectively) the easier it is to engage the clutch 10. Relatively large spaces between the teeth of the positive clutch 10, however, generally result in increased noise and vibration.
With reference to FIG. 2, it will be appreciated that the geometry of the clutch rings 12, 14 lend themselves to be discussed in radial coordinates. As such, each tooth of the plurality of teeth 16, 18 can occupy a certain amount of circumferential spacing on the clutch rings 12, 14. More specifically, each tooth, for example, can occupy a circumferential space of about twenty-eight (28) degrees (indicated by reference numeral 24) while the spaces 20, 22 therebetween (indicated by reference numeral 26) can occupy a circumferential space of about thirty-two (32) degrees. With this arrangement, there are six teeth with four degrees of clearance or lash between each tooth as shown in FIG. 2.
As noted above, it is easier to mesh the positive clutch 10 when there is more lash present, when compared to a similar positive clutch with less lash. More lash, however, causes the positive clutch 10 to produce noise and vibration due to the abundance of spacing between the teeth causing motion and clatter therebetween. To reduce noise and vibration, lash between teeth can be reduced. The reduction of lash, however, can also create additional noise and vibration due to the inability of the positive clutch to engage because each clutch ring 12, 14 of the positive clutch 10 will continue to rotate against one another and create noise and vibration until the positive clutch 10 engages.